Contributors to knee loading deficits during gait in individuals following anterior cruciate ligament reconstruction

Background: Altered gait mechanics following anterior cruciate ligament reconstruction (ACLr) are commonly reported in the surgical limb 2-3 months post-surgery when normalization of gait is expected clinically. Specifically, deficits in knee extensor moment during loading response of gait are found to persist long-term; however, the mechanisms by which individuals reduce sagittal plane knee loading during gait are not well understood. Research question: This study investigated between limb asymmetries in knee flexion range of motion, shank angular velocity, and ground reaction forces to determine the strongest predictor of knee extensor moment asymmetries during gait. Methods: Thirty individuals 108 +/- 17 days post-ACLr performed walking gait at a self-selected speed and peak knee extensor moment, peak vertical and posterior ground reaction force, and peak anterior shank angular velocity were identified during loading response. Paired t-tests compared limbs; Pearson's correlations determined associations between variables in surgical and non-surgical limbs; and stepwise linear regression determined the best predictor of knee extensor moment asymmetries during gait. Results: Reduced vertical and posterior ground reaction forces and shank angular velocity were strongly associated with reduced knee extensor moment in both limbs (r = 0.499-0.917, p < 0.005). Less knee flexion range of motion was associated with reduced knee moment in the surgical limb (r = 0.358, p < 0.05). Additionally, asymmetries in posterior ground reaction force and knee flexion range of motion predicted asymmetries in knee extensor moment (R2 = 0.473, p < 0.001). Significance: Modulation of kinetics and kinematics contribute to decreases in knee extensor moments during gait and provide direction for targeted interventions to restore gait mechanics.